It is known in the art to produce an airflow using electro-kinetic techniques, by which electrical power is converted into a flow of air without mechanically moving components. One such system is described in U.S. Pat. No. 4,789,801 issued to Lee (1988), depicted herein in simplified form as FIG. 1 and which patent is incorporated herein by reference. The system 100 includes an array of first (“emitter”) electrodes or conductive surfaces 112 that are spaced-apart symmetrically from an array of second (“collector”) electrodes or conductive surfaces 122. As shown the emitter array includes a single emitter electrode, but emitter arrays 110 having multiple emitter electrodes 112 are also described by Lee.
In this example, the positive terminal of a generator (e.g. a pulse generator) is coupled to the emitter electrodes, and the negative terminal of the generator is coupled to the collector electrodes. The pulse generator 140 outputs a train of high voltage pulses (e.g., 0 to perhaps +5 KV). The high voltage pulses ionize the air between the emitter and collector electrodes 112/122, and create airflow 150 from the emitter electrodes 112 toward the collector electrodes 122. Particulate matter 160 is entrained within the airflow 150 and also moves towards the collector electrodes 122. Much of the particulate matter 160 is electrostatically attracted to the surfaces of the collector electrodes 122, where the particulate matter 160 can collect, thus conditioning airflow 150 exiting the system 100. As a further benefit, the high voltage field present between the electrodes can release ozone into the ambient environment, which can eliminate odors that are entrained in the airflow.
In addition to particulate matter, volatile organic compounds (VOCs) can commonly be found in air. VOCs are petroleum-based chemicals found at elevated levels in most houses. Thousands of possible VOCs outgas from common household products. For example, VOCs can be released into the air by synthetic fragrances (as found in soaps, candles, air fresheners, incense and potpourri), paint, carpet, furnishings, glues, plastics, pressed wood products (such as plywood and particle board), and even fresh flowers and other items. Formaldehyde is a VOC that can be a particular problem in a home. Formaldehyde can be found in building materials, caulks and adhesives, paint, furniture, etc. When exposed to formaldehyde, it is not uncommon for a person to experience headaches, numbness or tingling of extremities, brain fog and inability to concentrate, anxiety, depression, etc. Further, formaldehyde is a sensitizing substance that can lower a person's threshold of sensitivity to other chemicals. Outgassing can be diluted by improving ventilation; however, where a source of formaldehyde and/or other VOCs is organic matter, such as mold, outgassing can be continuous and persistent. VOCs as outgassed waste products of mold can be more dangerous to an individual's health than mold spores drifting through the air.
In addition to producing side-effects in a sensitive individual, VOCs can produce noticeable odors. For example, the treatment process for many municipal water sources includes the addition of chlorine dioxide for use as a disinfectant. When a tap is turned on, the chlorine dioxide can diffuse into the air as the water is running. The chlorine dioxide can combine with VOCs found in the ambient air to produce compounds having unpleasant odors. The higher the levels of VOCs and chlorine dioxide, the higher the potential for odors. An odor problem will persist until VOC levels decrease. In enclosed areas with little ventilation, such as laundry rooms, basements, bathrooms and closets, such compounds accumulate, causing odors to be stronger and to linger longer than in well-ventilated areas.
One solution to VOC contamination is to clean and scrub air of VOCs. In air purifiers, air can be drawn through the purifier using fans and moved proximate to or through one or more carbon filters which absorb VOCs and odors. For example, a device using a high-efficiency particulate arrester (HEPA) filter typically draws large amounts of air through the HEPA filter using powerful fans. HEPA filters collect significant amounts of large particulate matter (0.3 μm and above) and can be coupled with a carbon filter that absorbs VOCs (and odors), removing VOCs from air passing through the HEPA filter. Such air purifiers can have limited effectiveness, however. The HEPA filter can have trouble collecting particulate matter smaller than 0.3 μm, and the carbon filter coupled with the HEPA filter eventually saturates and begins dumping VOCs and odors back into the environment.
Accordingly, there is a desire to improve upon existing electro-kinetic techniques by enabling existing electro-kinetic techniques to remove VOCs from air.